1. Field of the Invention
The present invention generally relates to a vehicle-mounted motor drive apparatus.
More particularly, the present invention relates to a safety motor drive apparatus adapted to perform a safety detection even when some object is caught in movable parts such as a power window and a sun roof or the like of a motor vehicle during a starting compensation time of a motor for opening and closing the movable part. Further, the present invention relates to a motor drive apparatus for a power window, which is used to perform and cancel an automatic operation of moving up and down the window of a motor vehicle.
2. Description of the Related Art
Generally, movable parts such as a power window and a sun roof or the like of a motor vehicle are usually opened and closed by driving motors. Further, such opening and closing of the movable parts are performed by operating a manual switch provided in the vehicle. Moreover, safety motor drive apparatuses for opening and shutting such movable parts as a power window and a sun roof or the like by means of motors perform safety operations of stopping or reversing the revolutions of motors immediately when some objects are caught in the movable parts, for the purpose of preventing a passenger or the like from being hurt by getting a part of his body caught in the movable part and also preventing a part of a motor and the like from being heated and damaged by getting a solid object caught in the movable part when opening and closing the movable parts, especially, when shutting the movable parts. In this case, a safety detection is to detect change in electric current (namely, motor current) flowing through a motor and to stop or reverse the revolutions of the motor as the result of the detection of abnormal large change in value of electric current flowing through the motor.
Meanwhile, in the case of a known safety motor drive apparatus, such a safety detection is not performed within a starting compensation time (usually, 100 msec or so) between a moment, at which the motor is started, and another moment at which the revolution of the motor becomes put into a stable condition, until the starting compensation time has elapsed.
Referring now to FIG. 4, there is shown a characteristic diagram for illustrating examples of change in motor current in the cases that the movable parts such as a power window and a sun roof or the like are normally opened and shut by means of motors and that the movable parts are opened and closed when some object is caught in the movable part.
In FIG. 4, the vertical axis and the horizontal axis represent motor current and time, respectively. In this figure, a period of time (namely, a time zone a) between moments t.sub.0 and t.sub.1 is a starting compensation time of a motor. Further, another period of time (namely, a time zone b) subsequent to the moment t.sub.1 is an operation time after the starting compensation time has elapsed, namely, a stable revolution time. Moreover, the solid line designates how the motor current changes in the case where the movable part is normally opened and closed. The dotted line denotes how the motor current changes in the case where an object is caught in the movable part during the starting compensation time (namely, the time zone a). Moreover, the one-dot chain line indicates how the motor current changes in the case where an object is caught in the movable part at the moment t.sub.2 in the stable revolution time (namely, the time zone b).
As shown in FIG. 4, in the case where the movable part such as a power window, a sun roof or the like is normally opened and closed, in the starting compensation time (namely, the time zone a), the motor current changes as follows. Namely, the current first starts increasing sharply at the moment t.sub.0 and thereafter the current starts decreasing abruptly past the middle thereof. Then, in the stable revolution time (namely, the time zone b) subsequent to the starting compensation time (namely, the time zone a), the motor current becomes kept almost constant. Further, when the movable part such as a power window, a sun roof or the like is opened and closed in the starting compensation time (namely, the time zone a) and the stable rotation time (namely, the time zone b), especially, in the case where some object is caught in the movable part when this movable part is closed in the starting compensation time (namely, the time zone a), the motor current becomes kept at a value close to the maximum current value thereof during the starting compensation time (namely, the time zone a). However, when the movable part is closed in the stable rotation time (namely, the time zone b), the motor current first increases to a specific value close to the maximum value thereof sharply, and thereafter the motor current is kept at such a specific value thereof.
Meanwhile, in recent years, a power window has come to be employed not only in a luxury car but in an ordinary car owing to its operability. Thus the power window has come into widespread use. Such conventionally known power windows are classified into two types according to the kind of a device for performing an automatic operation of moving up the window and canceling this automatic operation. Namely, a mechanically latching type and a relay latching type.
FIGS. 7A and 7B are block diagrams which illustrate the configurations of a device of the mechanically latching type and a device of the relay latching type, respectively and schematically.
As shown in FIGS. 7A and 7B, a power window switch 151 and a motor 152 for moving up and down the window in response to a switching operation, which occurs in this switch 151, are connected to a lock detecting circuit 153 for detecting a locked state of the window. An ignition circuit 154 for supplying driving power to the power window switch 151, the motor 152 and so on is connected to a mechanical latching mechanism 155 for latching the power window switch 151. This mechanical latching mechanism 155 is connected to a solenoid mechanical canceling mechanism 156 for canceling a latching operation of the mechanical latching mechanism 155. The solenoid mechanical canceling mechanism 156 controls the mechanical latching mechanism 155 according to a signal sent from the lock detecting circuit 153. An automatic latching relay 157 is connected to a latching circuit 158 which is operative to drive this relay 157. A canceling circuit 159 is operative to cancel an operation of this latching circuit to drive the automatic latching relay 157.
Further, the mechanical latching type device of FIG. 7A is operative to perform a mechanical latching of a solenoid by means of a mechanism element, to perform an automatic operation of moving up and down the window, to cancel the mechanical latching by means of the mechanism element and to cancel the automatic operation of moving up and down the window.
In contrast, the relay latching type device of FIG. 7B is operative to perform an automatic operation of moving up and down the window by means of an electronic circuit and to cancel the automatic operation by means of the electronic circuit.
As described above, a safety detection is effectively achieved in the safety motor drive apparatus when an object is caught in the movable part during the stable revolution time (namely, the time zone b) subsequent to the starting compensation time (namely, the time zone a) which is a period of time from a moment, at which the motor is started, to another moment at which the revolution of the motor becomes stable. Thus, predetermined safety functions are fulfilled. In contrast, when an object is caught in the movable part during the starting compensation time (namely, the time zone a), no safety detection is achieved. Thus, the predetermined safety functions are not fulfilled.
However, as illustrated in FIG. 4, electric current, the value of which is close to the maximum value thereof, flows through the motor during a period of time in the starting compensation time (namely, the time zone a), though such a period of time is short. Therefore, when some object, especially, a part of a passenger or the like is caught in the movable part such as a power window, a sun roof or the like in this starting compensation time (namely, the time zone a), it is feared that the passenger is sometimes injured seriously.
The present invention is accomplished to resolve such a problem.
Accordingly, a first object of the present invention is to provide a vehicle-mounted motor drive apparatus which is adapted to immediately stop the rotation of a motor if an object or the like is caught in a movable part during the revolution of the motor, thereby fulfilling safety functions.
Further, in the known mechanical latching type device for use in a power window apparatus, the solenoid should have a large canceling load so as to oppose the latch holding power of the mechanical latching mechanism 155. Moreover, the solenoid should inevitably have a large size so as to fully achieve an operation thereof against variation in supply voltage (ignition voltage) directly supplied from a car battery and in ambient temperature. Consequently, the known mechanical latching type device has encountered a problem that the size of a power window unit becomes large.
In contrast, the known relay latching type device can have a small-sized power window unit. However, in the case of the known relay latching type device, the automatic operation of moving up and down the window, as well as the canceling of such an automatic operation, is performed by using an electronic circuit. Thus, the electronic circuit picks up various kinds of noises generated in the interior of a motor vehicle. Consequently, the known relay latching type device has a problem that a malfunction occurs in the electronic circuit and therefore, the reliability of the power window is deteriorated.
The present invention is created to further eliminate this problem.
Therefore, a second object of the present invention is to provide a vehicle-mounted motor drive apparatus which is small in size and weight and has a small number of components and is insusceptible to variation in supply power and ambient temperature and to the influence of various kinds of noises.
Moreover, a third object of the present invention is to provide a vehicle-mounted motor drive apparatus which can quickly change a direction, in which a movable part such as a window is moved, to another direction when a selector switch for switching the direction is immediately operated at the time of commencing the movement of the movable part in a direction.